1. Field of the Invention
The present invention relates to a cover structure of a robot.
2. Description of the Related Art
A robot is used to carry a workpiece into a machine tool and to carry out the machined workpiece from the machine tool. A structure which protects the robot from a chip or a machining fluid is required in a case where the robot is used in an environment, such as a machining area of the machine tool, where the chip or the machining fluid scatters. For example, in a case where the robot automatically exchanges the workpiece of the machine tool, a system is generally configured such that a door separating the robot and the machining area is provided, the door is closed during machining, and the robot enters the machining area to exchange the workpiece when the door is opened after machining (see JP 2010-36285 A).
The door is necessary to be automatically opened and closed, and thus it is necessary to additionally prepare an actuator such as an air cylinder and to provide a control device such as an electromagnetic valve for driving the air cylinder through an electric signal sent from the robot or the machine tool. In addition, there is a risk that the robot collides with the door in a case where an erroneous operation occurs or the robot is operated more quickly than the opening/closing speed of the door.
In addition, a method in which the door is directly opened and closed by a hand of the robot can be adopted as another method of opening and closing the door. The actuator for opening and closing is not required in this case, but the method is not suitable for a high-speed motion by reason of the time loss according to an increase of the operation of the robot. In addition, there is still a possibility that an erroneous motion causes the robot to collide with the door.
FIGS. 1A and 1B illustrate a robot 1, which automatically exchanges a workpiece 13 mounted in a workpiece table 11 of a machine tool 7, and a structure of a door 4, which is automatically opened and closed, as an example of a conventional technology. The robot 1 is provided on an operation area A side, and includes an end effector 2 gripping the workpiece 13 at a fingertip. The operation area A and a machining area B are partitioned by a fixed wall 5. The door 4 is attached to the fixed wall 5, and is configured as an automatic door which can be opened and closed by an air cylinder 3. The machining area B of the machine tool 7 is blocked from the outside by the fixed wall 5 and the door 4.
The mechanical configuration of the machine tool 7 which machines the workpiece 13 is disposed in the machining area B. A tool main axis 9 is attached to a machine tool axis 8. Then, a tool 10 is mounted in the tool main axis 9. Reference numeral 12 indicates a scattered chip or cutting liquid 12 scattered when the workpiece 13 is machined. It is prevented that the chip or the cutting liquid is scattered toward the robot 1 in such a manner that the door 4 is closed as illustrated in FIG. 1A while the machine tool 7 machines the workpiece 13.
The door 4 is opened, and the robot 1 enters the machining area B as illustrated in FIG. 1B when the workpiece is exchanged after completing the machining. The air cylinder 3 is attached to the door 4, and air is supplied thereto (the device for supplying the air and the like are not illustrated) to open and close the door 4. A signal for opening and closing the door 4 is output from a control device (not illustrated) of the robot 1 or the control device (not illustrated) of the machine tool 7. For example, the electromagnetic valve (not illustrated) is controlled with the signal to switch the air to be supplied to the air cylinder 3 between ON and OFF.
A collision between an arm portion of the robot 1 and the door 4 occurs when the arm portion of the robot 1 enters the machining area B before the door 4 completely opens. It is necessary that a door detection sensor 6 perceiving an opening/closing state of the door 4 and the like are attached to limit the operation range of the robot 1 in order to prevent the collision.
In addition, there is also a method in which, for example, the robot 1 grips the door 4 with the end effector 2 to directly open the door 4 without using the actuator such as the air cylinder 3. This case does not require the actuator for opening and closing the door. However, a motion of opening and closing the door 4 is added so that it takes more time for the robot 1 to exchange the workpiece 13, and thus efficiency is decreased. This case also has a possibility that the erroneous operation occurs or the robot 1 is failed to open and close the door 4, and thus it is necessary that the door detection sensor 6 perceiving the opening/closing state of the door 4 and the like are attached to limit the operation range of the robot 1 in order to reduce the risk that the robot 1 collides with the door 4.